Process of making integral insulating board with hard welded surfaces



Patented July 7, 1931 UNITED STATES PATENT OFFICE WILLIAM H. MASON, OF LAUREL, MISSISSIPPI, ASSIGNOR TO MASONITE CORPORA- TION, OF LAUREL, MISSISSIPPI, A CORPORATION OF DELAWARE PROCESS OF MAKING INTEGRAL INSULATING BOASD WITH HARD WELDED SURFACES ll'oilh'awing'. Original appllcationflled March 1, 1926, Serial No. 91,447. Divided and this application filed March 16, 1928.

making an improved product, but for convenience refer herein especially 'to wood as a source of material.

The principal object of the invention is the production from natural wood, such as waste pieces from sawmills, of an integral its m board product, the interior or backing portion-of which is of relatively high porosity and is a good insulator, and the surface portion or portions whereof are hard, dense, stiff and strong, both the interior and surface portions being produced from an integral body of fiber.

Other objects will appear in the following description of my product and the process of aking.

The raw material, such as wood in small pieces or chips, is first converted into fiber. The fiber is preferably prepared by explosion from a gun through a constricted outlet or outlets under high pressure, preferably steam pressure, of about 250-1000# per square inch, but the wood may be ground or fibrated in other ways, so long as the lignins or a material part thereof are retained, and the fibers are not unduly chopped or shortened. Chemically digested fibers from which the lignins have been removed are not adapted for the purposes of my invention. To secure the best embodiment of my invention the fiber should contain all or practically all of the original wood or woody material disintegrated into fibrous state. Without commitment to a particular theory I believe that the lignins, which are plastic under conditions of heat, moisture and pressure hereinafter described, serve for producing a welding or coalescing of the cellulose fibers in the surface portion of my product solidly together, so that said surface portion for practical purposes consists practically of wood Serial No. 262,336.

remade in modified form, with the fibers rearranged without grain or order, and of increased density and hardness.

After being fibrated, as, for example, by explosion from a gun, refinement as by beatng and the like need not be resorted to and if there is any further refinement saine is not extensive. The exploded fiber direct from the gun can be made use of, if desired, for the purposes of the present invention, without refinement.

, The fiber is preferably formed into a felted sheet from a water bath, which may contain materials for making the product more waterproof or fire resistant or both.

Some of the excess water may be eliminated as by passing through squeezing rolls. This 1s, however, largely a matter of convenience, as the squeezing or wringing out of water, which takes place to some extent in any case in connection with the drying, can

all be performed in such connection.

In the fibration and formation in water into felted sheets or the like form, the natural substantially parallel arrangement of the fibers existing in the wood is lost and the fibers become criss-crossed in various directions, so that the resulting product is grainless and of substantially like-strength and stiffness in all surface directions.

The sheet or other form of fibrated material is subjected in moist form to heat and pressure. When in sheet form, the fiber sheet is cut into lengths as desired, and the sections introduced into a heated press, as, for example, for the production of products which are hard surfaced on both sides, be tween upper and lower steam heated press platens.

When the moist fiber sheet is compremd between the hot press platens, the pressure throughout the entire fibrous mass is subs'antially uniform, but the heat penetrates relatively slowly from the surfaces of the hot press platens toward the interior or center of the fibrous mass in the press. The welding of the cellulose fibers by their lignins appears to take place progressively inwardly beginning from the hot platen surfaces and extending gradually inward as the heat penetrates into the interior and toward the center of the mass of fiber. If the compression is sufliciently high and is maintained for a sufficiently long time to 5 permit the heat to penetrate throughout the mass of fiber, this welding action will be substantially complete throughout the entire thickness of the fibrous mass as is set forth and claimed in my copending application Serial No. 57 ,252, filed September 18, 1925-, issued as Patent Number 1,663,505 of March After an interval of time has elapsed, however, such that heat penetration and welding extends only part way in, and the welding is not yet complete all the way through, the mass of fiber between the press platens would be found to consist of hard,

dense, welded surface portions separated by an interior felted portion, which, while being subjected to the same pressure as the surface portions, has not yet become welded because of the heat not yet having penetrated sufficiently to produce welding in such reion. When the fibrous body is in this con- 'tion the application of heat is stopped or heat is reduced to a point below'the temperature required for welding or coalescing the fibers together, as for example by cutting oil the supply of steam to the press platens or'b introducing water therein. The inwar 1 progressive coalescing or welding of the fi rs is interrupted as mere application of rcssure is insufficient to produce the :5 effect of coalescing or welding of the fibers in the absence of sufficient heat. Upon openin the press at this stage, the central unwe ded portion will expand as the press platens are backed away, leaving the central portion of the sheet of porous, felted structure and well adapted for insulating p111- poses. No precautions need be observed in opening the press platens if the temperature is first sufliciently reduced to avoid blowing out or disruptive action of steam but the ress premure should desirably be continue for a time after the steam supply to the press platens has been cut off in order to ensure suitable reduction of temperature before releasing the press. Use of fiber in the form in which it comes from the gun without much or any refinement is advantageous by reason of its elastic nature and a good degree of interior rosity is. obtained by expansion of the unwel ed portion following pressure relief. j Pressures of from 200-700# per square inch, referably from 400500# per square tory results in producin surface portions of desirable hardness, density and strength, but

lwide variations in pressure, as from about 25120O# per square inch may be resorted to, if desired, to obtain density and strength in the surface portions corresponding roughly h f t' f me we been (mud to glve very'sa 18 M 'of high denseness and 'afbacking portion of to the pressure used. When steam heated press platens are used'the steam for heating the platens is preferably of a pressure over 50]: per square inch, but considerably higher pressures and temperatures than this may be used so long as objectionable overheating and charring is avoided. With press platens heated by steam at about 100# per square inch and a pressure between the platens of about 400-500# per square inch a fiber sheet which is about 1%" thick as it comes from the squeezing rolls after being subjected to the heat and pressure for about 5-10 minutes and the press released upon the temperature being reduced as described has a thicknesspf 4 approximately 1", of which the outer T or thereabouts on each surface is of hard, dense thoroughly consolidated and-welded structure and theintervening portion approximately in thickness is porous and of good insulating qualities. There can, of course, be a great deal of variation in respect of thicknesses and density of the product and the several portions thereof, according to requirements in connection with the use to which the board-is to be put, and the time of heat cut-off and release of the press is gauged in accordance with the particular sort of product required, the pressure being continued for a less interval where the thickness, strength and density of the surface portions is relatively less important and for longer periods when surface portions of greater resistin qualities are required.

In order to o tain desirably good welded i'oo surface portions, any give or shrinka e taking place in the body of fiber should followed up by the press platens, and the full pressure used should be maintained throughout the body of fibrous material, until the" point of time is reached at which theheat is cut down followed by-the pressure being intentionally released.

The drying is preferably completed, as, for example, in a drier or kiln after the sheetsfim are removed from the press.

A board as above described, and having upper and lower welded portions and an intermediate porous insulating portion is produced when the body-of feltedfiber is "'11: pressed between heated upper .and lower press platens. When, however, one of the pressplatens, as the lower one, is kept cold so that welding of the fibers does not take place in that part of the body offiber adja- 1 .cent to such cold platen and same expands after the. press is released, a board product is obtained having but one surface portion the por o us felted and non-welded fiber. The drying of the product-can readily be completed in the press after the pressure is wholly or partly released, as by restoring the steam which supply had been-cut oil to reduce the temperature prior toreleasing the press. a I claim:

1. Process-of forming integral fiber roducts comprisin adjacent portions whic are respectively 0 high density and of high porosity, which comprises applying heat and 1pressure to a body of moist ligno-cellulose her until welding or coalescing of the fibers into permanent relation has extended therein to a material extent but not therethrough, cutting off the application of heat while still maintaining the pressure, and finally releasing the pressure.

2. Process of forming integral fiber roducts comprising adjacentportions whic are respectively 0 high density and high porosity, whlch comprises a iplyggg heat and ressure to a moist body 0 w or woody ber, obtained b explosion from under a high pressure and containing practically all the original wood or woody material, untilwelding or coalescing of the fibers into permanent relation has extended therein to a material extent but not therethrou h, cutting off the application of heat while still maintaining t e pressure, and finally neleasing the pressure.

In testimony whereof, I have signed my WILLIAM H. MASON.

30 name hereto. 

